In a conventional relay, sometimes a pilot lamp is provided in order for a worker to easily check operation of a relay. The pilot lamp is provided in an upper portion of a housing of the relay so that the worker can easily visually recognize a lighting state of the pilot lamp.
FIGS. 1A and 1B are schematic sectional view and a schematic plan view of a conventional relay 11 incorporating a pilot lamp therein. In relay 11, a relay body 13 including a coil unit and a contact unit is assembled on a top surface of base 12, and relay body 13 is covered with a transparent housing 14 attached onto base 12. A Pilot lamp 15 constructed with an LED is provided in an upper portion of transparent housing 14. Pilot lamp 15 is lit when relay 11 is in an on state, pilot lamp 15 is turned off when relay 11 is in an off state, and an operating state of relay 11 can be checked by lighting on or turning off pilot lamp 15.
Because there is a need for downsizing of the relay, there is little room to allocate a sufficient space to provide pilot lamp 15 in transparent housing 14, thus pilot lamp 15 is arranged in a gap between relay body 13 and transparent housing 14 and an optical axis of pilot lamp 15 is horizontally oriented. Therefore, in relay 11, as indicated by a broken-line arrow in FIGS. 1A and 1B, the light emitted from pilot lamp 15 is inevitably interrupted in a certain direction by a member (holder 18) holding relay body 13 (for example, spring 16 and cable 17 of the relay body) or pilot lamp 15 in transparent housing 14. Accordingly, even if pilot lamp 15 is lit, the light emitted from pilot lamp 15 is hardly seen depending on the direction in which relay 11 is viewed, and sometimes the operating state of relay 11 cannot be checked. As illustrated in FIG. 1A, because the light emitted from pilot lamp 15 hardly passes through a corner portion of transparent housing 14, the light emitted from pilot lamp 15 can be hardly seen from this direction (oblique direction).
In the case that a plurality of relays 11 in FIGS. 1A and 1B are arrayed as illustrated in FIG. 2, for example, a light emission point (pilot lamp 15) of a right side relay 11 may be interrupted by transparent housing 14 of a relay 11 located on the left side of FIG. 2. Therefore, the light emitted from pilot lamp 15 is hardly recognizable from all directions.
Despite that pilot lamp 15 is a point light emission in relay 11 of FIG. 1, which makes the relay appear bright, the relay 11 will still be difficult to identify from another relay in the case when a plurality of relays is arrayed adjacent to each other. In particular, when the light emitted from pilot lamps 15 of one of the relays 11 is seen when it is transmitted through transparent housing 14 of the other relay 11, it will be hard to distinguish which relay is brightened. Additionally, because pilot lamp 15 is the point light emission, when disturbance light is reflected by the top surface of the relay, the light emitted from pilot lamp 15 is hardly seen when the disturbance light overlaps the light emitted from pilot lamp 15.
FIG. 3 is a perspective view of a relay 21 disclosed in Japanese Unexamined Patent Publication No. 2006-172731. In relay 21, a portion in which the relay body (not illustrated) is provided above base 22 is covered with cover 23. Rod-shaped light guide 24 extending in a vertical direction is provided in a side surface of cover 23, and the pilot lamp (not illustrated) is arranged inside cover 23 and opposite to an inclined surface on a bottom surface of light guide 24. The inclined surface on the bottom surface of light guide 24 constitutes reflecting surface 25. When the light emitted from the pilot lamp is incident to light guide 24 from a substantially horizontal direction, the light is reflected by reflecting surface 25 to bend an optical path upward, the light travels upward in light guide 24 is then output to outside the cover 23 from the top surface of light guide 24, known as a display surface 26. As a result, display surface 26 located in the top surface of relay 21 looks bright, and the operating state of relay 21 can be visually recognized.
In relay 21, because the top surface of relay 21 is brightened by guiding the light emitted from the pilot lamp using light guide 24 projected from the side surface, a point on an end of the top surface of relay 21 will appear bright. However, visibility is degraded when viewed from a side of a side surface opposite to the side surface through which light guide 24 allows light to pass, thus good visibility cannot be obtained when viewed from all directions.
In the case that a plurality of relays 21 are arrayed, when the top surface of a relay 21 is brightened, the light emission point is more visible behind an adjacent relay 21 compared with the relay 11 in FIG. 1. However, sometimes which relay is brightened is hard to recognize as it depends on the arrangement of the relays. For example, in the case that the relays are arrayed such that the side surfaces of the relays are opposite to each other, the light guide will be located between the relays adjacent to each other. Therefore, display surface 26 will look bright between the relays adjacent to each other, and which relay is brightened will be hard to distinguish from the other relays.
Because only a point of the end of the top surface of relay 21 appears bright, the light emission of relay 21 will be hard to see due to interruption of disturbance light caused by light reflection near the light emission point.